Re: [Haskell-cafe] Re: Debugging methods for haskell

On Sat, Jul 18, 2009 at 4:57 PM, Jon Fairbairn wrote:

Henning Thielemann writes:

...

On Thu, 16 Jul 2009, Fernan Bolando wrote:

...

Hi all

I recently used 2 hours of work looking for a bug that was causing

Program error: Prelude.!!: index too large

A good way to avoid such problems is to avoid partial functions at all. (!!) is also inefficient. Is it possible to define the function in terms of foldl?

I've looked at the code a bit more, and, with apologies to the original poster, it doesn't look much like Haskell. For example, in http://plan9.bell-labs.com/sources/contrib/fernan/escomma/Circuit.hs there's stuff beginning with

  tADM :: Int   tADM = 1

  tVSRC :: Int   tVSRC = 2

  tISRC :: Int   tISRC = 3

  ...

that I think probably should be

  data Something = ADM | VSRC | ISRC ... deriving (Enum, ...)

though when I get to "(((fst z0)!!pMSET)!!pMTYPE) == mOP" I'm at a loss to determine quite what the intention is. Maybe it should be an array indexed by enum types, maybe a function, maybe something that can be pattern matched on? I don't know.

The intention is z0 is a system parameter and database, it contains a set of info needed to define a particular simulation it looks like ( [n,m...], [m,o,p]) n is is a list info settings for the circuit analysis m is a list of statistics for the circuits that is need in sub-sequent calculation m is a list of circuit settings like temperature etc. o is a list of matrix solution for non-linear newton raphson p is a list of matrix solution for time dependent calculations the bug was in o this is a variable length [Double] whose length depends on the size of matrix bieng solved. so. (((fst z0)!!pMSET)!!pMTYPE) == mOP is checking if we are doing mOP type calculations. If this was C this would be a structure of settings and buffer data. fernan -- http://www.fernski.com